With the release of the “First Report and Order,” Feb. 14, 2002, by the Federal Communications Commission (FCC), interest in ultra wide bandwidth (UWB) communication systems has increased. UWB communication systems spread information over a wide bandwidth of at least 500 MHz. Due to this spreading operation, the power spectral density, and thus the interference to narrow bandwidth receivers is small.
For impulse radio signals, pulse-position modulation, (PPM) and pulse amplitude modulation (PAM) are the most popular signaling techniques. These techniques are combined with time hopping (TH) for multiple-access format. In TH, each symbol is represented by a series of ‘basis pulses’. The locations or delays of the pulses are determined by a TH code at the transmitter. The TH hopping code is generated as a pseudo-random sequence.
In TH impulse radio, a set of frames (Nf) frames are allocated for each transmitted symbol. In each the frames of the set, one ultra-wideband pulse is transmitted during a chip interval. To recover the transmitted symbols from the pulses in the set of frames, samples from the set of frames need to be combined in order in order to achieve a lowest bit error probability (BEP).
It is desired to provide a linear receiver for a time-hopped, impulse radio system that combines samples of pulses received over a frequency selective channel optimally, in a multi-transmitter environment.